This invention relates to a continuous annealing process for metals, such as cold reduced steel, strip coil and the like, and more particularly to such a method having increased heating efficiency, increased productivity and simplicity and apparatus therefor.
Generally, for example, cold reduced strip coils are annealed in a batch box type furnace wherein the coils are charged as a tight or open coil in a single stack or in multiple stacks. It is well known, that there are many difficulties in prior art annealing equipment and progress in improvements has been slow and in small steps, with, however, each small step being significant. Prior art methods and apparatus have various deficiencies and difficulties of operation of the furnace and handling of the coils to be annealed and after annealing. Consequently, there are considerable deficiencies and problems in addition to non-uniformity of annealing operations. For example, many of the difficulties in operation of the furnace are encountered because both the heating and cooling of the coils are performed in the same fixed furnace chamber. One difficulty is due to the construction of the annealing furnace, which roughly comprises a base, an outer cover, an inner cover, and other attached equipment. Some of the above parts must be re-arranged at the time of cooling of the fully heated coils from their positions used for the heating cycle. This is usually done by a crane. Disadvantageously, such method results in inefficiencies of heating and loss of production time. For example, the heat for the heating cycle is lost after the heating cycle and also added energy is necessary to cool the coil in the same chamber.
Moreover, such a method requires furnances which are disposed close together in a narrow annealing yard. Thus, the coils to be annealed and the coils already annealed are usually placed in overcrowded areas. Consequently, the coils tend to become damaged. Furthermore, there are other difficulties, such as sticking together of the stacked coils due to increase of coil weight, difficulty in arranging the treatment of combusion expelled gases, etc. Thus, the operation of prior furnaces and controlling of coils are plagued by various problems and inefficiencies.
Various counter-measures have been proposed and used in the prior art. An example is the so-called "U.A.D." system by Lee Wilson Company, Ltd. This system does not use a crane, and instead opens and closes a door to a single furnace chamber in which both the heating and cooling are carried out. Through the door, the coil is charged using a cart. But, this prior art system uses the same chamber to both heat and cool; thus, the prior art problems of low productivity and low heating efficiency are still present and unresolved.